A multicenter clinical trial whose primary objective is to compare the safety and efficacy of 3 therapeutic regimens for AIDS-related CMV retinitis in patients treated with foscarnet or ganciclovir and whose retinitis progressed or recurred. Also, the safety and efficacy of continuing to treat patients with same anti-CMV drug versus being switched to the alternative drug as a result of randomization will be compared to those assigned by randomization to continue treatment with the same drug.